She nodded.  “I shall find him all right.”  She slipped the envelope inside her dress, and glanced at the watch she was wearing on her wrist.  “There are several things I wanted to tell you,” she added, “but they none of them matter for the moment.  If I go at once, I can just catch the three-thirty.”

“I’ll come as far as the road with you,” I said.  “I daren’t leave the hut for long, in case McMurtrie turns up.”

We went outside and had a good look round.  Sonia had long since disappeared, and the place wore its usual aspect of utter desolation.  I took the precaution of locking the door, however, and then at a sharp pace we set off together across the marsh.

“Tell me about George,” I said.  “How are you getting on with the elopement plan?”

Joyce smiled.  “I think George is growing a little impatient.  He wants to get away as soon as possible.”

“Yes,” I said; “I have no doubt the Mediterranean sounds attractive to him.  There’s a pretty stiff penalty attached to selling Government secrets if you happen to be found out.  Besides, I expect he’s still worrying a lot about me.”

Joyce nodded.  “He told me last night that I was the only thing that was keeping him in London.  You see I can’t quite make up my mind whether I love him well enough to come away.”

“That’s unfortunate for George,” I said.  “Latimer will probably act at once as soon as he gets that letter, and directly he does I mean to go straight to Cheyne Walk, unless I’m dead or in prison.”

Joyce took my arm.  “Neil,” she said, “whatever happens you mustn’t be arrested.  If you think there’s any chance of it you must go on board the Betty and take her somewhere down the river.  You can let me know at the flat where you are.  Promise me you will, Neil.  You see if the police once got hold of you, even Latimer mightn’t be able to do anything.”

For a moment I hesitated.  So far I had told Joyce nothing of the wild suspicion about Marks’s identity which Sonia’s revelations had put into my head.  I didn’t want to rouse hopes in her which might turn out quite baseless.  Besides, even if I were really on the right track, and Marks was the man who had betrayed the gang in St. Petersburg, it was quite another thing to prove that they were responsible for splitting his skull.  I had nothing to support the idea beyond Joyce’s bare word that she had seen McMurtrie in the flat on the afternoon of the murder.  Sonia’s testimony might have been useful, but after today I could hardly picture her in the witness-box giving evidence on my behalf.

On the whole, therefore, I thought it best for the present to keep the matter to myself.  I promised, however, that in the event of my observing anything in the nature of a policeman stealthily approaching the hut I would at once seek sanctuary on the Betty—­an assurance which might have sounded worthless to some people, but certainly seemed to comfort Joyce.